1. Field of the Invention
The present invention relates to a method for formatting, and managing defective areas of a rewritable optical recording medium.
2. Description of the Related Art
In general, repetitively rewritable optical recording media, i.e., optical disks may be sorted into CD-RW (Rewritable Compact Discs) and rewritable digital versatile discs (DVD-RAM, DVD-RW and DVD+RW). In these rewritable optical disks, information writing/reading thereto/therefrom is performed repetitively according to typical use of the optical disk. The repetitive write/read of information causes a change of a mixing ratio from an initial mixing ratio of a recording layer mixture provided for recording the information, which leads to a loss of initial properties of the mixture. Such loss causes errors in writing/reading information, which is called degradation. Areas of the degradation are turned up as defective areas when formatting, writing or reading of the optical disk is carried out. Other than such degradation, defective areas of the rewritable optical disk are caused by scratches on a surface, dust, and/or production defects. Therefore, in order to prevent writing/reading data to/from the defective areas formed by the foregoing causes, management of the defective areas is required. To do this, as shown in FIG. 1, DMAs (Defect Management Areas) are provided in a lead-in area and in a lead-out area of the optical recording medium (for example, DVD-RAM) for managing the defective areas of the optical recording medium. And, data areas are managed in groups, each having a user area for actual writing of data thereon and a spare area for use in a case of defect occurrence in the user area. In general, there are four DMAs provided in one disk (for example, a DVD-RAM), two in the lead-in area and the other two in the lead-out area. As management of the DMAs is important, the same data is repeatedly written in the four DMAs for protection of data. Each DMA has two blocks having 32 sectors total, i.e., one block has 16 sectors. A first block (called as a DDS/PDL block) of each DMA has a DDS (Disc Definition Structure) and a PDL (Primary Defect List), and a second block (called as an SDL block) of each DMA has an SDL (Secondary Defect List). The PDL denotes a primary defect data storage, and the SDL denotes a secondary defect data storage.
In general, the PDL stores entries of defects which occurred during fabrication of the disk, and all defective sectors identified in formatting, i.e., initializing and re-initializing, the disk. As shown in FIG. 2A, each entry has an entry type and a sector number of a defective sector.
The PDL is further divided into a P-list, a G1-list, and a G2-list. Defective sectors defined by disk fabricators, for example defective sectors from a disk fabricating process, are stored in the P-list. Defective sectors found during a certification process are stored in the G1-list. Defective sectors transferred to the SDL directly without the certification process are stored in the G2-list. The entry type indicates an origin of the defective sector occurrence, for example, if the entry type is xe2x80x9810bxe2x80x99, the origin of the defective sector occurrence is sorted to be P-list, and if the entry type is xe2x80x9810bxe2x80x99, the origin of the defective sector occurrence is sorted to be G1-list, and if the entry type is xe2x80x9811bxe2x80x99, the origin of the defective sector occurrence is sorted to be G2-list.
On the other hand, the SDL, listed in block units, stores entries of defective areas occurring after formatting, or defective areas which cannot be listed on the PDL during formatting. As shown in FIG. 2B, each of the SDL entries has an area for storing a sector number of a first sector of a block having the defective sector therein and an area for storing a sector number of a first sector of a replacement block to replace the defective block. Initialization of the disk includes initialization and re-initialization. During re-initialization, full formatting, such as an initial formatting, occurs including partial certification in which the initialization is done partially, and an SDL is transferred to the G2-list in the PDL. A conversion of the SDL to G2-list (called a simple formatting hereafter), without certification shortens the duration of formatting. The P-list is unchangeable by any formatting. Since the defective blocks on the SDL are stored as in units of sectors (i.e., all sectors in a xe2x80x9cdefectivexe2x80x9d block), the G2-list may contain good sectors as well as the defective sectors which cause the block to be xe2x80x9cdefective.xe2x80x9d
For example, as shown in FIG. 3A, in the partial formatting, sectors on the P-list and the G1-list before formatting remain on the P-list and the G1-list as they are, and the old G2-list and defective blocks listed on the SDL before formatting go through a certification process. After all entries on the G2-list and SDL are erased, only defective sectors found in the certification process are listed on the G1-list. The defective blocks listed on the G2-list or the SDL may also include sectors without defects. If the G1-list overflows, the rest is listed on a new SDL, and the G2-list has a null data inserted therein.
As shown in FIG. 3B, in the simple or quick formatting in which the SDL is converted into the G2-list without a certification process, sectors on the P-list, G1-list and G2-list before formatting are maintained on the P-list, G1-list and G2-list as they are after formatting. The old SDL entries are converted into 16 PDL entries, and listed on the G2-list after the old SDL entries are erased. In this instance, if the G2-list overflows, the rest of the SDL entries not listed on the G2-list are listed on a new SDL. The overflow occurs because the number of entries which can be listed on the PDL is limited by a DMA processing condition. The following equation (1) shows one example of the DMA processing condition.
SPDL+SSDLxe2x89xa616 sectors (1xe2x89xa6SPDLxe2x89xa615, and 1xe2x89xa6SSDLxe2x89xa615)xe2x80x83xe2x80x83(1)
                    where        ,                                                  S            PDL                    =                      ⌊                                                            (                                                                                    E                        PDL                                            xc3x97                      4                                        +                    4                                    )                                +                2047                            2048                        ⌋                          ,        and                                xe2x80x83                                      S          SDL                =                              ⌊                                                            (                                                                                    E                        SDL                                            xc3x97                      8                                        +                    24                                    )                                +                2047                            2048                        ⌋                    .                    
SPDL is a number of sectors used for maintaining PDL entries; SSDL is a number of sectors used for maintaining SDL entries, EPDL is a number of PDL entries; and ESDL is a number of SDL entries. And, └P┘ for some real number P denotes the greatest integer not greater than P. That is, the equation (1) determines a number of total sectors which can be used both for PDL and SDL, and that number cannot be greater than 16. A number of sectors which can be used either for PDL or SDL cannot be greater than 15.
In the meantime, the defective areas (i.e., defective sectors or defective blocks) in the data area should be replaced with good areas, according to a slipping replacement algorithm or linear replacement algorithm.
Referring to FIG. 4A, in the slipping replacement which is applicable to a case when a defective area is listed on the PDL, if the defective sector is present in the user area on which an actual data is to be written, the defective sector is skipped, and instead, the data is written on a good sector next to the defective sector. Therefore, the user area having the data written thereon is pushed back to occupy as many spare areas as the skipped defective sectors, at the end. That is, the user area slips into the spare area as many as the sectors listed on the PDL.
And, referring to FIG. 4B, in the linear replacement which is applicable to a case when a defective area is listed on the SDL, if a defective block is present in the user area, the defective block is replaced with block units of replacement areas assigned to the spare area in writing the data. If the replacement block listed on the SDL is found to be defective later, a direct pointer method is applied to the SDL. That is, by the direct pointer method, the defective block is replaced with a new replacement block and the SDL entry having the defective replacement block listed thereon is corrected. However, because the linear replacement requires shifting the optical pickup from the user area to the spare area and shifting the optical pickup from the spare area back to the user area, such repetitive shifting may result in a poor system performance.
One of the reasons for reformatting is to improve system performance by transferring the defective sectors listed on the SDL to the PDL, thereby reducing continuous linear replacement. The reformatting may be conducted according to a variety of methods. As the formatting is complicated, there is a trend to simplify the formatting, such as the simple formatting in which the SDL is converted into G2-list without certification. However, the simple formatting in which the SDL is converted into G2-list without certification causes the PDL to approach the DMA processing condition shown in the equation (1) faster because all the sectors of the defective blocks listed on the SDL are converted into G2-list. This is liable to cause overflow from the DMA. For example, as the SDL entry has 8 bytes and the PDL entry has 4 bytes, if one SDL entry is converted into the G2-list of the PDL, the PDL requires 64 (=4xc3x9716) bytes. In this instance, if the overflow occurs, a case when the disk cannot be used any more may occur, and the simple formatting impedes making the most use of the DMA.
Accordingly, the present invention is directed to a method for formatting, and managing defective areas of a rewritable optical recording medium that substantially obviates one or more of the problems due to limitations and disadvantages of the related art.
Additional features and advantages of the invention will be set forth in the description which follows, and in part will be apparent from the description, or may be learned by practice of the invention. The objectives and other advantages of the invention will be realized and attained by the structure particularly pointed out in the written description and claims hereof as well as the appended drawings.
To achieve these and other advantages and in accordance with the purpose of the present invention, as embodied and broadly described, a method for formatting an optical recording medium includes transferring information on defects listed on a secondary defect list (SDL) to a primary defect list (PDL); and listing only information on first sectors of defective blocks from the SDL on the PDL.
Another embodiment of the invention includes a method for formatting an optical recording medium, including transferring information on defects from a secondary defect list (SDL) to a primary defect list (PDL) in either block or sector units based on a predetermined indication; and listing the information in block units or sector units on the PDL based on the indication.
It is to be understood that both the foregoing general description and the following detailed description are exemplary and explanatory and are intended to provide further explanation of the invention as claimed.